Patriot confused about one set up (8)
I believe the answer is:
loyalist
'patriot' is the definition.
(I've seen this before)
'confused about one set up' is the wordplay.
'confused' becomes 'lost' (synonyms).
'about' is an insertion indicator.
'one' becomes 'ilay' (I can't explain this - if you can you should believe this answer much more).
'set up' is a reversal indicator (in a down clue, letters go up).
'ilay' reversed gives 'yali'.
'lost' enclosing 'yali' is 'LOYALIST'.
Can you help me to learn more?
(Other definitions for loyalist that I've seen before include "Person faithful to the government, like Orangeman in N Ireland" , "One true to a cause" , "Patriot" , "One true to monarch or government" , "supporter of ruler" .)